It has heretofore been generally proposed to employ laser-initiated explosive energies in fabrication of integrated circuits. In Cranston U.S. Pat. No. 3,727,296, for example, small charges of explosive material, such as azide or fulminate explosives, are deposited on the free ends of integrated circuit leads which are cantilevered over a substrate. The explosive material is ignited by laser energy to propel the lead ends against the underlying substrate with sufficient force to bond the leads to the substrate. In order to detonate explosive materials, a minimum quantity of explosive is necessary. This minimum quantity is determined at least in part by the so-called deflagration to detonation distance, which is the distance required for an ignition shock front to propagate to explosive detonation. Thus, the technique proposed in Cranston is both difficult to control on the scale therein disclosed, and is not amenable to use on a smaller scale, such as in fabrication of the integrated circuits themselves. There is also a problem of explosion by-products.
Frish et al, "Surface Coating and Alloying by Laser Induced Heat and Pressure," Final Report, NSF Grant No. DMR-8260087 (May 1983) and "Metal Bonding with High Intensity Laser Pulses," SPIE Proceedings, Vol. 458 (Jan. 1984) propose bonding metal foils to substrates of dissimilar metal by placing the foil in contact with the substrate and then irradiating the foil surface remote from the substrate with a laser pulse so as to ablate a portion of the foil surface. Thermal and pressure waves are generated in the foil and travel through the foil thickness at differing velocities. If the thermal wave reaches the foil/substrate interface during irradiation, both materials will melt and thereafter mix under the influence of the laser-induced pressure gradients. Thus, the disclosed "laser stamping" technique makes use of both heat and pressure supplied to the foil by the high intensity laser pulse.
Drew et al T988007 (1979) discloses a laser vapor deposition technique wherein a CW laser beam is directed through a transparent substrate onto a reservoir of metal on the opposite side of and spaced from the substrate. The laser beam heats and vaporizes the metal of the reservoir, which is then redeposited on the opposing surface of the substrate.
Mayer et al, "Plasma Production by Laser-Driver Explosively Heated Thin Metal Films," J. App. Phys., 57, February 1985, pp 827-829, discloses a technique for producing metal vapor clouds or plasmas for studying laser/plasma interactions. A thin metal film on the surface of a glass substrate is irradiated by a short laser pulse directed through the substrate. The laser energy is absorbed by classical skin-depth absorption to rapidly heat and "explode" the film from the substrate preferentially along an axis perpendicular to the substrate surface. A high-power second laser beam is thereafter directed into the resulting metal vapor plasma to heat the plasma and thereby provide opportunity for controlled study of laser/plasma interactions.